How can I use Filter nodes from Compositor in Material Editor?
Unfortunately, compositing nodes and shader nodes are not interchangeable.

There are some new shader nodes available in the 2.81 release, which include extra vector math and the ability to connect inputs to the mapping node.

If these are not adaptable to your needs, you will need to do what you want in the compositor. Using cycles, you can use the object and material indices to get a mask in the compositor allowing you to apply the dilate to a specific object/s.

While the object and material indices are not currently available in evee when compositing, they are available in the object info shader node. You could use layers to have one object separated from the scene so you can adjust it in the compositor before combining it into the final image.